Helicenes: Synthesis and Applications

Shen, Yun; Chen, Chuan‐Feng

doi:10.1021/cr200087r

Cited by 1,276 publications

(1,093 citation statements)

References 545 publications

Supporting

Mentioning

1,025

Contrasting

Unclassified

Order By: Relevance

“…Similarly, 1-(2-hydrosilylphenyl)naphthalene derivatives were converted to the corresponding sila [4]helicenes 2c and 2d in 95% and 90% yields, respectively. Sila [5]-and sila [6]helicenes 2e and 2f were also obtained, although a slightly higher temperature (135 o C) was required for the transformations due to the higher steric repulsion compared with that of sila [4]helicenes. The substituents on the silicon center were also variable, and diphenylsilane afforded the corresponding sila [6]helicene 2g in slightly lower yield compared with the reaction of dimethylsilane 2f.…”

Section: Scheme 1 Comparison Of Reactivitymentioning

confidence: 99%

“…By selecting the proper ligands, the current method provides the ability to prepare unsymmetrical sila[n]helicene derivatives without any oxidants. The resulting sila [6]helicene is a rare example of a five-membered ring-fused [6]helicene, which was isolated as a single pure enantiomer without substituents on the terminal benzene rings.…”

mentioning

confidence: 99%

“…6 In addition to a unique function as an optoelectronic material, these compounds can be utilized as ligands and organocatalysts. 6c Despite their promising potential for functional materials, few [n]helicenes could allow customization of their properties, and dehydrogenative silylation with the activation of ubiquitous CH bonds is thought to allow a more straightforward approach.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Synthesis and Properties of Sila[n]helicenes via Dehydrogenative Silylation of C–H Bonds under Rhodium Catalysis

et al. 2016

View full text Add to dashboard Cite

Use of a rhodium catalyst with (R)-(S)-BPPFA ligand allows efficient synthesis of sila [n]helicenes via dehydrogenative silylation of CH bonds. By selecting the proper ligands, the current method provides the ability to prepare unsymmetrical sila [n]helicene derivatives without any oxidants. The resulting sila[6]helicene is a rare example of a five-membered ring-fused [6]helicene, which was isolated as a single pure enantiomer without substituents on the terminal benzene rings.Silicon-containing -conjugated molecules show promise as materials useful in the areas of electro-and photoluminescence. 1 The incorporated silicon atom has a significant impact on the energy levels of the frontier orbital, and that of the LUMO is effectively stabilized by the interaction between the low lying * orbital of two exocyclic -bonds of the silicon atom and the * orbital of the conjugated -system of the backbone. Catalytic dehydrogenative silylation of CH bonds is a straightforward, atom-efficient, and sustainable route toward these silicon-containing -conjugated molecules. 2-5 Since our first report in 2010 on the synthesis of silafluorenes, 3a rhodium-catalyzed dehydrogenative silylation has been developed for the synthesis of various silicon-containing -conjugated molecules, such as silicon-bridged p-terphenyl, 3a spirosilabifluorenes, 3b,3j benzosilolometallocenes, 3e-g dihydrobenzosilole, 3i and phenazasilines 3d (Figure 1). To further demonstrate the utility of this silylative cyclization, development of a robust catalyst system with improved reaction efficiency is highly desirable for the synthesis of more challenging siliconcontaining -systems. The present paper describes the synthesis of sila[n]helicenes (n = 4, 5 and 6) with uniquely merged -conjugated systems of helicene and silole. This study also demonstrates that the amino group-substituted (R)-(S)-BPPFA ((R)-N,N-dimethyl-1-[(S)-1',2-bis(diphenylphosphino)ferrocenyl]ethylamine) ligand is highly effective for the rhodiumcatalyzed dehydrogenative silylation of CH bonds.Helicene possesses a unique screw-shaped -system consisting of all ortho-annelated aromatic rings. 6 In addition to a unique function as an optoelectronic material, these compounds can be utilized as ligands and organocatalysts. 6c Despite their promising potential for functional materials, few [n]helicenes could allow customization of their properties, and dehydrogenative silylation with the activation of ubiquitous CH bonds is thought to allow a more straightforward approach. We previously reported that Wilkinson's catalyst, RhCl(PPh 3 ) 3 , is effective for the silylative cyclization of 2-(2-

show abstract

Section: Scheme 1 Comparison Of Reactivitymentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Synthesis and Properties of Sila[n]helicenes via Dehydrogenative Silylation of C–H Bonds under Rhodium Catalysis

et al. 2016

View full text Add to dashboard Cite

show abstract

“…Helicenes are important molecules in asymmetric catalysis and material science, but have never been synthesized with a terminal pyrrole ring to the best of our knowledge. [19] Scheme 3. Further transformations of the alkynylated indole products.…”

Section: %mentioning

confidence: 99%

“…The results obtained with PtCl2 and PtBr2 were difficult to reproduce, probably due to the poor solubility of reagent 4a in CH3CN. Using a co-solvent led to more reproducible results (entries [17][18][19]. THF was the best, giving the desired product 8a in 96% yield (entry 18).…”

mentioning

confidence: 99%

Platinum‐Catalyzed Domino Reaction with Benziodoxole Reagents for Accessing Benzene‐Alkynylated Indoles

Waser

2015

Angew Chem Int Ed

View full text Add to dashboard Cite

Indoles are omnipresent in natural products, bioactive molecules and organic materials. Consequently, their synthesis or functionalization are important fields of research in organic chemistry. Most works focus on installation or modification of the pyrrole ring. To access benzene ring-functionalized indoles with an unsubstituted pyrrole ring remains more challenging. Herein we report a platinumcatalyzed cyclization-alkynylation domino process to obtain selectively C5-or C6-functionalized indoles starting from easily available pyrroles. Our work combines for the first time a platinum catalyst with EthynylBenziodoXole (EBX) hypervalent iodine reagents in a domino process for the synthesis of polyfunctionalized arene rings and gives access to important building blocks for the synthesis of bioactive compounds and organic materials.Functionalized indoles occupy a privileged position in organic chemistry, as they can be found in biomolecules, drugs, agrochemicals and materials. [1] To access these important building blocks, a first approach consists in the introduction of functional groups onto simple, commercially available indoles. In order to have a more efficient alternative to well-established cross-coupling reactions, the transition metal-catalyzed direct functionalization of C-H bond on indoles has been intensively investigated in the last two decades. Nevertheless, this approach is mostly limited to the modification of the more reactive pyrrole ring (innate reactivity, Figure 1, A). [2] The functionalization of the benzene ring has been only rarely achieved and is limited to C2,C3-disubstituted indoles. [3] One notable exception is the selective iridiumcatalyzed C7-borylation of indoles reported by Hartwig and coworkers. [4] We were particularly interested by the introduction of an alkyne onto the benzyl ring of indoles, as alkynes are key building blocks in medicinal, synthetic and material chemistry. [5] Direct alkynylation approaches can be used only to access 2-and 3-substituted indoles. [6] This is an important limitation, as 5-or 6-alkynylated indoles can be found in bioactive compounds such as 5-LOX (5-lipoxygenase) inhibitor 1, [7a] or NMDA (N-Methyl-DAspartate Receptor) antagonist 2. [7b] Alkynylated carbazoles are especially important for organic materials, such as macrocycle 3, an organic sensor for the detection of TNT. [7c] If an efficient method for the synthesis of benzene-alkynylated indoles can be developed, more complex compounds could then be easily obtained by using wellestablished C-H functionalization at the C2 or C3 positions or transformations of the triple bond. As C-H metalation of the arene ring of indoles is extremely difficult in presence of the more reactive C2 and C3 C-H bonds, we wondered if the desired reactive intermediate could be generated in situ during a metal-catalyzed cyclization step (Scheme 1). The use of such "domino" or "cascade" processes is one of the most efficient ways to increase molecular complexity in organic synthesis, [8] but it had not y...

show abstract

Structure and Property Diversity of Chiral Helicene Oligomers

Saito

Shigeno

Yamaguchi

2015

Encyclopedia of Polymer Science and Technology

View full text Add to dashboard Cite

alkylthio, and perfluoroalkyl groups. In addition, cyclization of helicene oligomers provides another method of obtaining diversity.A notable aspect in the diversity of helicene oligomers is that they can be connected to provide multidomain oligomers (Fig. 4). When two helicene oligomers are connected, they are referred to herein as homo-bidomain oligomers. Cyclic homo-bidomain oligomers are also conceivable. Hetero-multidomain oligomers can be obtained by connecting different structures of oligomers. Such manipulations provide a large diversity of structures.Because helicene can generate characteristic π−π interactions, helicene oligomers often form bimolecular, trimolecular, tetramolecular, and polymolecular aggregates in which homoaggregation and heteroaggregation can also occur. Such aggregates self-assemble to form fibrils, vesicles, liquid crystals, and surface monolayers. These noncovalent bonding interactions provide diversity of the structure of helicene oligmers. Diverse Properties of Helicene OligomersStructural diversity is directly related to diversity of properties, and the properties of a helicene oligomer can be varied by structural modifications. In addition, multidomain oligomers can be designed, in which properties A and B of each domain can be combined. Such compounds exhibit property A + B or even another property C, a result regarded as the "synthesis of a property or function." Aggregation and self-assembly of helicene oligomers further increase property diversity, which covers materials with a broad range of sizes from subnanometersized molecules through nano-and micrometer-sized molecular aggregates and molecular self-assemblies to macroscopic bulk materials. Helicene oligomers are sensitive to changes in the environment such as temperature, solvent, and concentration. Different properties appear in dilute solution, in concentrated Amidohelicene oligomers: (a) acylcic oligomers (P)-1 (n = 1−9) with dianiline spacer, cyclic oligomers (P)-2 (n = 1−10) with dianiline spacer, (b) acyclic oligomers (P)-3 (n = 1−9) with m-phenylene spacer, and acyclic reverse oligomers (P)-4 (n = 1−4). (c) Schematic representation of reversible change between helix dimer and random coils of (P)-3 and (P)-4. solution, in the crystalline state, in the amorphous state, on the solid surface, at the solid-liquid interface, in fiber assemblies, in liquid crystals, and in gels. Dynamic properties of helicene oligomers are also interesting, and structural changes are largely affected by the environment, providing a stimulus response or possible molecular switching materials. It is also noteworthy that the process of a structure change can produce unusual transient phenomena. Amidohelicene OligomersStudies on helicene oligomers were initiated with amide derivatives (Fig. 5a, top), in which the spacer has a bent shape and includes both hydrogen bonding donor and acceptor moieties (24). (P)-5,8-Helicenedicarboxylate was reacted with bis(2,6-dimethylanilino)cyclohexane to give a series of acyclic helicene oligomers 1 up t...

show abstract

Helicenes: Synthesis and Applications

Cited by 1,276 publications

References 545 publications

Synthesis and Properties of Sila[n]helicenes via Dehydrogenative Silylation of C–H Bonds under Rhodium Catalysis

Synthesis and Properties of Sila[n]helicenes via Dehydrogenative Silylation of C–H Bonds under Rhodium Catalysis

Platinum‐Catalyzed Domino Reaction with Benziodoxole Reagents for Accessing Benzene‐Alkynylated Indoles

Structure and Property Diversity of Chiral Helicene Oligomers

Contact Info

Product

Resources

About